Classifications

• • G—PHYSICS
  • G06—COMPUTING; CALCULATING OR COUNTING
  • G06F—ELECTRIC DIGITAL DATA PROCESSING
  • G06F16/00—Information retrieval; Database structures therefor; File system structures therefor
  • G06F16/20—Information retrieval; Database structures therefor; File system structures therefor of structured data, e.g. relational data
  • G06F16/27—Replication, distribution or synchronisation of data between databases or within a distributed database system; Distributed database system architectures therefor
  • G06F16/273—Asynchronous replication or reconciliation
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S707/00—Data processing: database and file management or data structures
  • Y10S707/99951—File or database maintenance
  • Y10S707/99952—Coherency, e.g. same view to multiple users
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S707/00—Data processing: database and file management or data structures
  • Y10S707/99951—File or database maintenance
  • Y10S707/99952—Coherency, e.g. same view to multiple users
  • Y10S707/99953—Recoverability

Definitions

• the present invention relates generally to communications systems and, in particular, to techniques that provide for synchronizing databases, such as a database containing a phonebook stored in a subscriber identity module (SIM) of a mobile terminal used in a cellular radiocommunication system with a corresponding database in a personal computer (PC).
• SIM subscriber identity module
• PC personal computer
• the communication link 30 may be either a wire or wireless (e.g., infrared) link. It will be appreciated by those skilled in the art that, while a PC and mobile phone are used as examples of two devices between which database synchronization may be performed, the present invention is not limited to 'these two types of devices and may, in fact be applied to database synchronization between any two types of devices, such as electronic organizers, pagers, and the like.
• the PC 10 includes a database 40, for example, containing phone records or a calendar, while the mobile phone 20 includes a corresponding database stored on its subscriber identity module (SIM) card 50.
• SIM subscriber identity module
• the SIM card 50 is a removable smart card ⁇ that was created for the GSM radiocommunication standard as a mechanism for conveniently grouping and storing information elements related to the mobile subscriber in a removable manner, which card is insertably removable from mobile phones.
• synchronize as it is used herein to refer to database operations associated with two or more devices, means changing the contents of one database so that it matches, or "mirrors", the contents of the other database.
• the change log contains information regarding records which t , have been operated upon in either database subsequent to synchronization therebetween.
• the change log also records the time at which a synchronization operation was last performed between two databases, so that changes made prior to a previous update can be ignored.
• the change log can be implemented, for example, in a portion of memory which records for each change an event (e.g. , add, delete or modify), the identity of the database record for which the event occurred and a timestamp indicating when
• change log 210 may be advantageous during synchronization since only those records which have been modified, added or deleted (as recorded in the change log) since the last synchronization update need to be transmitted between the devices. Thus, the synchronization process may be performed more rapidly and this process has, therefore, been referred to as "fast synchronization".
• the change in DID values acts as a signal that tells the device performing database synchronization to use full synchronization instead of fast synchronization.
• the receiving device e.g. , a PC
• compares the DID received from the other device e.g., a mobile phone
• fast synchronization will be used. If they are different, then full synchronization is performed.
• fast synchronization relies on the use of a time stamp associated with each entry in the change log 200, 210.
• the time stamp indicates what time a particular change was made.
• the synchronization engine within the other device uses the timestamp to resolve potential conflicts that can occur when one modification has been made to an entry in one of the databases and a different modification has been made to the same entry but in the other database. In such cases, the rule is to assume that the most recently made change is the correct one.
• FIGS. 3 and 4 illustrate some scenarios in which changing the clock on a device can cause erroneous results to occur when a subsequent database synchronization operation is performed.
• this timing diagram shows clocks and events in each of two devices, denoted "Device 1" and “Device 2" .
• the clocks in both devices read " 1:00pm", at which time a fast database synchromzation operation is performed. As mentioned earlier, this causes, among other things, the time of synchronization to be recorded in the change log 200.
• T2 the clock in Device 1 has been set back, so that it now reads 12:00pm (i.e., a time earlier than 1:00pm).
• the clock in Device 1 indicates 8:00pm, and the clock in Device 2 indicates 9:00pm.
• T3 another fast database synchronization operation is performed between the respective databases in Device 1 and Device 2.
• the synchronization engine looks at the timestamps in the change log 200, and ignores all changes that appear to have taken place prior to the previous • synchronization operation (which took place at time T3).
• FIG. 4 illustrates another scenario in which changing the clock on a device can cause erroneous results to occur when a subsequent database synchronization operation is performed.
• this timing diagram shows clocks and events in each of two devices, denoted "Device 1" and “Device 2” .
• the clocks in both devices read "1:00pm", at which time a fast database synchronization operation is performed.
• this causes, among other things, the time of synchronization to be recorded in the change log 200.
• the value of the clock in Device 1 is subsequently moved forward, so that at time T2, it reads 3:00pm while the clock in Device 2 only reads "2:00pm”.
• the clock in Device 1 is again changed, this time backward, so that at a time denoted T3, it and the clock in Device 2 both read 2:30pm.
• T3 a fast synchronization operation is again performed between the databases in Device 1 and Device 2.
• the timestamp associated with the change to record "A" at time T2 indicates that the change took place at 3:00pm (i.e., a time later than the present time of 2:30pm)
• the change to record "A" is ignored in the synchronization operation, effectively losing this data.
• the foregoing and other objects are achieved in methods, apparatuses and computer readable storage media that synchronize a. first database with a second database, wherein the first database is located in a mobile terminal. Synchronization comprises setting an indicator to indicate that a full synchronization should be performed in response to detecting that a timer in the mobile terminal has been set back. Then, a full synchronization of the first database with the second database is performed if the indicator is set.
• the indicator may be data dedicated to that purpose.
• setting the indicator may instead comprise changing a value of a database identifier. Since the database identifier will be communicated between the two databases anyway, no additional information needs to be communicated merely for the purpose of indicating that a full synchronization should be performed. If the indicator is not set, a fast synchronization of the first database with the second database may instead be performedr
• the indicator may be reset after performing the full synchronization of the first database with the second database.
• FIG. 1 is a block diagram that illustrates a conventional technique for synchronizing databases between devices
• FIG. 2 is a block diagram that illustrates a modification of the technique and system of FIG. 1, wherein change logs are introduced into each device for synchronizing the database;
• FIG. 3 illustrates a scenario in which changing the clock on a device can cause erroneous results to occur when a subsequent conventional database synchronization operation is performed
• FIG. 4 illustrates a scenario in which changing the clock on a device can cause erroneous results to occur when a subsequent conventional database synchronization operation is performed
• FIG. 5 is a flowchart that illustrates exemplary steps that may be performed by a synchronizing entity to select which type of synchronization to perform, in accordance with the invention
• FIG. 6 is a flowchart depicting steps to be performed by a device to ensure that a full, rather than a fast, synchronization operation will be performed when necessary.
• any such form of embodiment may I e referred to' herein as "logic configured to" perform a described action.
• fast synchronization may be the type of synchronization that is performed in most instances. Invoking full synchronization of two databases when fast synchronization is available may then been accomplished by providing some type of indicator to the synchronizing entity, instructing that a full synchronization should be performed.
• indicator may take the form of, for example, a random or incremental change in the value of the database identifier (DID) which is passed between the devices as part of the synchronization process.
• FIG. 5 is a flowchart that illustrates exemplary steps that may be performed by a synchronizing entity to select which type of synchronization to perform.
• the synchronizing entity relies on two indicators: a locally generated indicator (LOCAL SYNC-TYPE), and one that is provided by the other device (REMOTE SYNC-TYPE). The reason why there are two indicators is because the device that initiates the synchronization process may not be the same device that has determined that a full, rather than a fast, synchronization operation is called for.
• LOCAL SYNC-TYPE locally generated indicator
• REMOTE SYNC-TYPE REMOTE SYNC-TYPE
• DID database identifier
• Such embodiments have an advantage in that the DID value is usually one of the parameters that are exchanged between databases as part of the change log. Thus, the need to further exchange additional parameters (i.e., sync type indicators) can be eliminated.
• the particular strategy adopted in any particular system is not critical, and may be left up to the individual designer. For the sake of simplicity, the exemplary embodiment utilizes indicators that are dedicated to this purpose.
• a LOCAL SYNC-TYPE indicator is retrieved, for example from a local memory device (step 501).
• retrieving the LOCAL SYNC-TYPE indicator may mean comparing a present DID with a DID that was saved at the time,, of the last synchronization operation.
• the indicator provided by the other device (REMOTE SYNC-TYPE indicator) is received as well (step 503). The values of the two indicators are then tested. For example, the LOCAL
• SYNC-TYPE indicator may be tested first (decision block 505). If it indicates that a full synchronization is required ("YES" path out of decision block 505), then the LOCAL SYNC-TYPE indicator is returned to its default value (i.e., set to indicate that a fast synchronization should be performed) (step 507) and a full synchronization is performed (step 509). Setting the LOCAL SYNC-TYPE indicator to its default value ensures that, unless express actions are taken to do otherwise, the default operation will be performed the next time a synchronization operation is invoked.
• the REMOTE SYNC-TYPE indicator is tested (decision block 511). If the REMOTE SYNC-TYPE indicator indicates that a full synchronization should be performed ("YES" path out of decision block 511), then a full synchronization operation is performed (step 509).
• a full synchronization operation should be performed if it follows a change in which the device's timer is set to an earlier time. It is also permissive, but not required, for a full synchronization operation to be performed if it follows a change in which the device's timer is set to a later time. This will ensure that synchronization will not be dependent on timestamp values, but instead will be done by comparing records between the two databases, one-at-a-time.
• FIG. 6 is a flowchart depicting steps to be performed by a device to ensure that a full, rather than a fast, synchronization operation will be performed when necessary.
• a test is performed to determine whether the device's local timer value has been adjusted to an earlier value (decision block 601). If it has ("YES" path out of decision block 601), then the local sync-type indicator is set to indicate that a full synchronization operation should be performed (step 603). Otherwise, this step is skipped ("NO" path out of decision block 601).
• the sync-type indicator may take the form of a changed DID value. The invention solves the "time trip" problem, thereby making it possible to utilize timestamps for database synchronization.
• the solution may not be optimal, but it has the advantage of preventing the loss of data. Every time the user changes the time on the device (or at least, every time the user changes the time on the device to an earlier time), a full synchronization is performed, in which all data stored on the device is read, and compared to the other device's database. Differences are identified and updated on both devices. For those conflict situations in which a same record has been modified in the databases of both devices without any ability to accurately determine which modification is the most recent, a policy of always selecting- the record from a particular one of the devices (e.g. , always using the modification that was made on the PC) can be adopted.

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• Engineering & Computer Science (AREA)
• Theoretical Computer Science (AREA)
• Databases & Information Systems (AREA)
• General Physics & Mathematics (AREA)
• Physics & Mathematics (AREA)
• General Engineering & Computer Science (AREA)
• Data Mining & Analysis (AREA)
• Computing Systems (AREA)
• Mobile Radio Communication Systems (AREA)
• Telephonic Communication Services (AREA)
• Stabilization Of Oscillater, Synchronisation, Frequency Synthesizers (AREA)
• Synchronisation In Digital Transmission Systems (AREA)
• Information Retrieval, Db Structures And Fs Structures Therefor (AREA)
• Information Transfer Between Computers (AREA)

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• 2000
  • 2000-08-25 US US09/645,305 patent/US6718348B1/en not_active Expired - Lifetime
• 2001
  • 2001-08-21 ES ES01965203T patent/ES2278774T3/es not_active Expired - Lifetime
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